Zn-0.7 wt.% Cu-hypoperitectic alloy was prepared in a graphite crucible under a vacuum atmosphere. Unidirectional solidification of the Zn-0.7 wt.% Cu-hypoperitectic alloy was carried out by using a Bridgman-type directional solidification apparatus under two different conditions: (i) with different temperature gradients (G = 3.85–9.95 K/mm) at a constant growth rate (41.63 μm/s) and (ii) with different growth rate ranges (G = 8.33–435.67 μm/s) at a constant temperature gradient (3.85 K/mm). The microstructures of the directionally solidified Zn-0.7 wt.% Cu-hypoperitectic samples were observed to be a cellular structure. From both transverse and longitudinal sections of the samples, cellular spacing (λ) and cell-tip radius (R) were measured. The effects of solidification-processing parameters (G and V) on the microstructure parameters (λ and R) were obtained by using a linear regression analysis. The present experimental results were also compared with the current theoretical and numerical models and similar previous experimental results.

The effects of hydrogen-charging on tarnishing film-induced brittle cracking of brass were studied. The tarnishing film was generated on brass samples with various hydrogen concentrations in Mattsson’s solution, then removed from the solution, dried, and subjected to a slow loading rate (loading speed = 0.5 mm/min) in air. The results indicated that hydrogen caused the film-induced brittle cracking to be more difficult to occur and a considerably high concentration of hydrogen could inhibit completely the film-induced brittle cracking. Elastic modulus test results showed that elastic modulus of the brass substrate decreased and elastic modulus of the tarnishing film increased with increasing the hydrogen concentration. Hydrogen inhibiting the film-induced cracking can be ascribed to the fact that hydrogen changed the elastic modulus of substrate and film.

Ambient temperature α-to-β phase transition and nanocrystallization in the aged Ti–25Nb–3Mo–3Zr–2Sn titanium alloy was achieved by surface mechanical attrition treatment (SMAT). The phase transition occurs at α/β interfaces and extends to α phase interiors with increasing strain. It is irreversible and diffusion controlled. The stress-induced increase of Gibbs energy and enrichment of Nb may cause a high order of lattice instability of the α phase adjacent to the α/β interfaces and compel the α phase to β phase. The presence of fine α needles in the aged alloy and the phase transition from α to β with increasing strain are viewed to play a crucial role in the subsequent nanostructuring.

A series of molecular dynamics simulations was performed to study grain boundary sliding of three types of [101¯0] tilt grain boundaries in a magnesium bicrystal. In particular, a near Σ11 twin boundary, an asymmetric near Σ11 twin boundary, and a θ = 40.3° general [101¯0] tilt grain boundary were studied. Simulations showed that grain boundary sliding (a rigid motion of two grains relative to each other along boundary plane) did not occur over the stress range applied; instead, coupled shear motion (grain boundary sliding induced boundary migration) was dominant. Although the measured coupling coefficient, the ratio of boundary tangential displacement to boundary normal displacement, was in good agreement with theoretical prediction, the detailed shear behavior was different, depending on types of grain boundary, magnitude of applied shear stress, and temperature. It was also noted that grain boundary twining was the predominant mechanism that allowed the coupled shear motion to occur in hexagonal close-packed (HCP) magnesium.

Allotropic hexagonal-close-packed (hcp) → face-centered-cubic (fcc) transformations were reported in Group IVB elements titanium (Ti), zirconium (Zr), and hafnium (Hf) subjected to mechanical milling in a high-energy SPEX shaker mill. Although the transformation was observed in powders milled under regular conditions, no such phase transformation was observed when the powders were milled in an ultrahigh purity environment by placing the powder in a milling container under a high-purity argon atmosphere, which was in turn placed in an argon-filled glove box for milling. From a critical analysis of the results, it was concluded that the hcp → fcc phase transformation was, at least partially, due to pick-up of interstitial impurities by the powder during milling of these powders to the nanocrystalline state.

Here we describe a simple method to produce boron nanoparticles with control over surface chemistry and dispersiblity in different solvents, with potential applications ranging from high energy density fuels to neutron capture therapy. The methodology should be adaptable to many hard materials; indeed, we have produced hydrocarbon-dispersible silicon nanoparticles using a procedure similar to that described below. The method, based on high-energy milling, with subsequent sedimentation to separate aggregates, produces gram quantities of nanoparticles in a narrow distribution of particle sizes centered around 50 nm, and should be readily scalable to industrial scale production.

Intense debates have been prompted concerning whether homogeneous deformation can be achieved in bulk metallic glasses at room temperature through the suppression of shear bands at the submicron scale. In this short communication, we demonstrate that multiple shear banding can be successfully attained via a proper modification of the microsample geometry, resulting in the appearance of a homogeneous deformation mode at the submicron scale. However, the apparent deformation homogeneity in our microcompression experiment is a manifestation of the sample geometry effect on the propagation rather than nucleation of shear bands.